Electrical power to a trailer pulled by a tractor is provided by connecting the tractor electrical power supply to a number of dedicated electrical circuits associated with the trailer, typically through an electrical connector on the front of the trailer commonly referred to as a “nosebox.” Conventionally, the trailer includes dedicated circuits for the left-turn signal, right-turn signal, signal markers, taillights, stoplights, the antilock brake system (ABS) control circuit and ground. Tractor-trailer fleets have conventionally used the circuit adapted for use for powering the ABS control circuit for auxiliary applications, such as for providing power to interior trailer lights (e.g. so-called trailer “dome” lights), whenever the ABS control circuit is not to be utilized, such as when the trailer is parked. U.S. Regulation FMVSS 121 allows other lamp functions to use the ABS power line; however, the owner/operators of the vehicle have a responsibility to make sure the ABS braking system has the proper available amperage/voltage to operate properly when braking. The owners/operators therefore demand a system be implemented that will ensure that power is removed from the trailer auxiliary power circuit when the trailer is in motion.
Prior art systems for accomplishing this rely on signals transmitted from the tractor to the trailer to indicate when the trailer is in motion and, consequently, that power should be removed from the trailer auxiliary power circuit. For example, U.S. Pat. No. 5,739,592 entitled Power and Communications Link Between a Tractor and a Trailer requires a communication line between the tractor electrical system and the trailer electrical control module in order to control application of dedicated power to the ABS circuit. Similarly, U.S. Pat. No. 7,286,046 entitled Systems and Methods for Supplying Power to a Vehicle Trailer includes a module in the trailer that monitors the brake light signal from the tractor in order to determine when power may be supplied to the trailer auxiliary power circuit. These and other prior art systems therefore add complexity to the trailer by requiring additional wiring to allow monitoring of signals that indicate when the trailer auxiliary power circuit may be energized.
There is therefore a need for a system and method to ensure that power is removed from the trailer auxiliary power circuit when the trailer is in motion without requiring the coupling of external control signals to the controller. The present disclosure is directed toward systems and methods which meet this and other needs.